Cape Cod Insulation Advice

Bob W._3

You could start here:

http://www.homeenergy.org/consumerinfo/index.html

I recall their web site had some article on how to insulate and seal a Cod; not easy. Unvented attics seem to be the new thing. Also check the Building Envelope Program (BEP) at ORNL. http://www.ornl.gov/sci/roofs+walls/index.html

Another edit: You could check out Lstiburek's latest tome at this site: http://www.eeba.org/mall/builder_guides.asp I think he has done some writing on the subject.

John S.

Not sure how to vent and insulate my cape cod

Hello all,

I recently purchased a cape cod style house built in 1927 and would like to optimize/upgrade the attic ventilation and insulation. However, I'm quite confused as to how the roof has managed not to buckle due to lack of ventilation.

The rafters & ceiling joists in the attic are both part of a 2x4 truss system. The rafters themselves have been insulated (at least 40 years ago?) with foil side down fiberglass from soffit through a 3 1/2" area spanning almost 8' (between plaster & roof decking) all the way up to the ridge. It appears that the soffits are packed with insulation and never had any venting. My understanding is that the rafter insulation is a 'no-no', however, the dead men had their ways.

I, somehow, never have a problem with ice buildup or premature roof failure, however, I seem to lose a fair amount of heat. I know that windows & walls are another factor, but could someone give me an idea as to how to optimize the venting/insulation combination in the attic?

The only current vents are the roof vents up near the ridge. I have thought about introducing gable-type vents on each end of the house as low as possible to introduce more airflow.

I have attached a sketch of the current situation.
Your expert advice is very much appreciated.

John S.

Bob W

Thanks for the links. I wasn't able to find anything detailed about Cape Cod style homes specifically, but there's lots of good info there.

Anyone else have any input?

joel_19

insulation

Roof rafters for insulation is the way to go if it's done right esp in the crawl spaces of capes . pay attention to the crawl spaces . In many of them you can look between the floor joists and see all the way across to the other side . these should be blocked so air can not travel across . Go to www.comfortinstsitute.org and find a contractor there who can do ablower door test for you.

Bob W._3

Here is a Home Energy/Lstiburek article on Unventing Attics in Cold Climates; I don't know if it is still on their website but I found the web address on a printout:

http://homeenergy.org/archive/hem.dis.anl.gov/eehem/99/991111.html

Here is the article on insulating various home styles. Took awhile but I found it:

http://homeenergy.org/archive/hem.dis.anl.gov/eehem/98/980508.html

You can look at all their archived articles at the above address, ending with eehem/

Gordy

Cape Code

John S. Its fun doing a little detective as to the why things were done as they have been. Are the existing vents in each rafter bay? Does the side of the house without roof vents face north? Is there existing soffit venting? What about shading from trees. A combination of things may be the reason why your roof has stood the test of time from improper practices. Is it possible,upon closer inspection that there is a slight gap between the roof deck and foil back insulation? If so then that gap may follow through to the soffits allowing some air flow. But the lack of roof vents on the one side of the roof would not allow flow in the rafter bays on that side of the roof.

Obviously the majority of your heat loss in the roof deck appears to be in that 8' section,and side walls. About all you could do there is take out the fiberglass and pump a high R foam in the rafter bays, Or fir those 8' sections down another 3 1/2", and add some foam re drywall that portion.

Easiest way to see your higher heat loss areas on your roof is after a early morning of frost or light snow. Look at your roof and see what has melted first. Then if you know of a neighbor with a well insulated roof compare yours to that.


You really did not indicate how far you wanted to go with this.


Gordy